1. Field of the Invention
In a general sense, the invention is related to systems achieving nuclear fusion reactions at large-scale for economical generation of power by fusion reactions only, generation of power by driving sub-critical fission piles with neutrons from fusion reactions, and production of neutrons for other applications including but not limited to pulsed neutron beams for research, medical applications, etc. In addition, the techniques for generating ion beams needed to ignite fusion may be used together or singly to increase the intensity of ion beams for various applications.
2. Background Information
The heavy ion driver defined in 1975-1976 by R. L. Martin and A. W. Maschke used the known abilities of high-energy RF (radiofrequency) accelerator systems to store megaJoule quantities of ion beam energy and to focus this stored energy on very small spots. They saw that the short stopping distance of beam nuclei with high atomic number (Z) at approximately one-half the speed of light meant being able to create the energy density in small targets containing fusion fuel that is needed to ignite small clean-fusion explosions. And they showed that the continuous stored beams could be rearranged into multiple bunches, compressed in length, and delivered to the targets in short duration pulses as required by the dynamics of the fusion ignition and burn processes.
Beams of protons can be accumulated—and stored—over a long period of time, as the protons resist processes that cause them to wander from their controlled paths, such as knock-on or multiple scattering, and have low probability of changing their charge to 0 (neutral) or negative (H−). On the other hand, the probability of the charge state of a heavy ion changing by collision with an atom remaining even in a very high vacuum requires ignition pulses be generated in a fraction of a second. This is consistent with the need for an ICF (inertial confinement fusion) power plant reactor to pulse frequently, and pulsing many times per second is routine for accelerator systems. However, the need to generate an ignition pulse within a limited time places a constraint on the accelerator technology that eliminates slow pulsing machines like synchrotrons.
Thus, at the inception of heavy ion fusion (HIF), a few principles were established:                GeVs of energy in each ion provided means to generate beam pulses to ignite ICF burn with: much more total beam energy than competing technologies, the tight focusing required by the dimensions of fusion fuel pellets, the beam power required for ignition with beam currents obtainable with confirmed processes;        Rearrangement of the total beam for an ignitor pulse into the short time duration required for the fuel compression and ignition processes is the technical issue;        The question for economics is the cost of large particle accelerators, which does not fit conventional ideas of electric power generation or the motivations for research neutron sources;        One accelerator has the ability to produce many times the output of a conventional power plant, which results in low cost per unit of energy;        Favorable economics is obtained by capitalizing on this by using the high-grade heat at high temperatures to produce hydrogen and synthesize liquid fuels and lower the cost of other energy-intensive industries such as steel and aluminum;        These economics apply to using the neutrons from the fusion reactions to drive fission reactions in sub-critical fission piles, and        Portions of the neutrons from the fusion and/or fission reactions can be provided for research, production of isotopes for applications in medicine and other purposes.Current Amplification Processes Used to Generate Heavy Ion Fusion Ignition Pulses        
Accelerating heavy ions solved the problem of depositing the megaJoules of beam energy in small targets containing fusion fuel. The beam energy also must be delivered to the fuel targets in pulses with the short durations, e.g. of the order of 10 nanoseconds, consistent with the timescale of igniting small fusion explosions by rapidly compressing and heating to ignition so that fusion burn is effected before the compressed and heated fuel is able to fly apart. Using processes verifiable by the same analytical tools at the root of the design of all successful accelerators, Martin, Maschke, and others defined examples of systems to reconfigure the beams and deliver them to the target on this time scale.
The physics of particle beams employs mathematical methods that characterize the motion of the particles that make up a beam; “a collection of particles confined in space”, in the terms of statistical physics. Pertinent to the present matter is the concept of beam emittance, a property that is conserved and thus a “constant of the motion”, reference being to the progress of the beam through the accelerator and beam transport system. The emittance of a beam determines the diameter of the focal spot, to the 0th order, i.e., before accounting for such spot-size increasing effects as aberrations. By the statistical physics, the physical beams obey theorems holding that the emittance of a beam of identical particles cannot be decreased by any conservative, i.e., reversible, operation on them through external forces. That is, the emittance when a beam is born is the best (lowest) it can be. The emittance can and does grow in real machines, the design of which takes care to minimize the causes of such deleterious effects.
In slightly more general terms, the 6-dimensional phase space of a beam is conserved. The six dimensions are the positions of the particles in the three conventional physical dimensions and the particles' relative momentum components. Planes are defined in the phase space with the position and momentum components for coordinates, with time used in the place of the position coordinate in the direction of the beam's motion. The area occupied by the beam particles in each of these planes is the beam's emittance in that plane.
The physics teaches that the sums of the emittances in the three planes remains constant, under the action of purely conservative external forces, and some of the area of the emittance in one plane may be traded to one of the others, or shared with both.
“Ballistic” focusing of charged particle beams is analogous to focusing beams of light: the spot size depends on the emittance, of the particle's paths coming into the electromagnetic lens, aberrations from beam parameters (such as the momentum spread) inherent in the ideal optics, and imperfections in the magnetic fields of the lens. For example, the effect of focusing a particle beam that has a range of momentum per particle is similar to the “chromatic” aberration of focusing light with a variety of wavelengths (or photon energies, or “colors”), shown visibly in the spectrum from a prism, and the term chromatic aberration also is used in “particle beam optics”.
The term “brightness” characterizes the intensity of the number of beam particles contained in the beam's 6-dimensional phase space. As the phase space volume occupied by the beam particles cannot shrink, the beam brightness cannot be increased by conservative forces, during the “motion”. The brightness can and does decrease in real machines as a result of any loss of beam particles in addition to distortions of the beam that increase its effective emittance.
Ignition of inertially confined fusion reactions requires a beam that is extremely powerful, contains a substantial quantity of kinetic energy to be deposited in the target to generate the high pressure required to drive the fuel to densities a hundred times the fuel's normal solid density. The ability to provide the unimprovable beam brightness at the source and preserve enough of it during subsequent acceleration and beam manipulations to meet the demands of compressing the fuel (a.k.a. implosion) is the bedrock of heavy ion fusion driver technology.
The goal of the design of HIF drivers is to manipulate the beams so that the relatively low beam current at beam inception, at the source, which is limited by the electro-magneto dynamics of the particles whose like electrical charge creates mutually repulsion forces tending to enlarge the beam in physical space. Expert evaluation of the first HIF system concepts to be proposed confirmed the judgment that HIF driver systems could be built and operated to deposit energy in the required target volume and mass and in the short allowable time to achieve ignition.
This judgment, however, assumed an adequate concentration of expert effort would be applied to arrive at designs that would accomplish the mission. Resources adequate for this effort have not be provided, and the most vital HIF efforts continue the struggle via dual-purpose application of resources provided to continue the advance of particle accelerator systems for research. This has placed the development of the capable HIF drivers at risk of overlooking machine design approaches that necessitate concentration on only beams comprised of heavy ions in a low charge state (lightly ionized), preferably with q=1, where q is the number of electrons removed from the neutral atoms. This kind of concentration has yielded the novel features of the single pass RF driver concept.
A review of the existing state of the art will preface description of the SPRFD's new features. A shorthand means to summarize the net effect of the several individual current amplification processes proposed during the intense vetting of HIF “point” designs in 1975-80, was the following equation:Itarget=Isource×Nsources×Ninjection×Ncompression×Nbeams_on_target.  (1)
The total beam power on the target is the product of the total current of particles (the same as the electric current for q=1, etc.) and the kinetic energy per particle. Ignitor pulse power of ca. 1 PW (1 petaWatt is 1 billion megaWatts) is needed for ignition. This can be provided, for example, by some number of beams of 20 GeV ions with an aggregate current of 50 kA (kiloAmperes). Early HIF driver concepts using mainstream RF accelerator technology were judged capable of meeting the requirements promulgated by leading implosion experts. A problematic factor related to the use of storage rings (which contribute the factor Ninjection in Equation 1.) is described below. This problematic situation is resolved in the SPRFD by the absence of storage rings, also as described below.
Another means of amplifying the eventual current (introduced in 1978 by Burke) accelerates ions of multiple isotopes. This method effectively multiplies the 6-dimensional phase space available to the designer, since each isotope is a different particle species, and thus not subject to the constraint of Liouville's theorem. The advantageous effect of multiple isotopes is that a given set of parameters for energy deposition in the fusion target can be accomplished with 1. a set of beams that are each comprised of a different isotope (which are different species (kinds) of particles whether these are isotopes of the same atomic element, e.g. xenon, or different atomic elements, e.g., xenon and lead), to allow each isotopic beam to have lower brightness than would be required if the energy deposition requirements were to be met by a number (the factor Nbeams in Equation 1.) of beams all comprised of the same particle species. The motivation for the multiple isotope technique was to gain design margin by raising the capabilities of the beam, to drive implosion of fusion fuel “pellets”, beyond the marginal implosion abilities that were the targets of the early designs. In the arena of the energy supply industry where capital costs are large, reducing risks of unacceptable performance is mandatory at the conceptual level. The power of multiple beams may be regarded as relieving pressure on other techniques for beam amplification/compression/compaction. However, the potential ways to use this additional design factor to best advantage were not aggressively explored, and only formally adopted in the internationally vetted “point” design called Heavy Ion Driven Inertial Fusion (HIDIF) in 1995-97.
The means of compacting beams that have been devised to meet the ignition requirements for inertial confinement fusion also may be used singly or in various combinations to increase the intensity of ion beams for beneficial applications.
Power production using only fusion reactions can be shown to be the most desirable of any baseload energy source, using inclusive metrics including abundance, safety, environmental impact, and cost. It is widely recognized, however, that a shortfall in fusion energy produced from a given amount of energy used to drive the reactions may be compensated by causing the neutrons produced in the fusion reactions to induce fission reactions in a suitable mass of fissionable fuel. This construct is called the fusion-fission hybrid. This construct has potential advantages including the safety aspect in that the fission pile would be sub-critical, since the need to emit slightly more than one neutron per fission reaction is not needed. This feature plus the high energy of the fusion neutrons and their high fluxes enables this construct to be devised to destroy high level radioactive waste in the process of generating power. If desired, in a limiting case of this application, a HIF hybrid system could be totally dedicated to destroying radioactive waste.
To use neutrons from fusion reactions for applications such as research and production of special isotopes, beams of neutrons in collimation channels provided for the purpose may be directed into moderators to achieve the neutron spectra desired for these applications. The beams also may be directed into a neutron multiplying material or a sub-critical mass of fission material to: 1. Increase the total number of neutrons available that that point for the intended applications, 2. Exchange lower energy neutrons for the high energy fusion neutrons, and 3. Be integrated with the moderator as previously said.